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BKDR_KELIHOS.CEW

August 14, 2013
 Analysis by: Nikko Tamana
 ALIASES:

Backdoor:Win32/Kelihos (Microsoft), W32/Kelihos.BC!tr (Fortinet)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware


This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It executes commands from a remote malicious user, effectively compromising the affected system.

  TECHNICAL DETAILS

File Size:

1,221,269 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

09 Aug 2013

Payload:

Connects to URLs/IPs, Steals information, Drops files, Collects system information, Sends messages

Arrival Details

This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Autostart Technique

This backdoor adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
{Random Value} = "{Malware Path and File Name}"

Backdoor Routine

This backdoor executes the following commands from a remote malicious user:

  • Request spam email messages structure and template
  • Send spam email messages
  • Send stolen information
  • Get operating system information
  • Get drive information
  • List running processes
  • Download and execute arbitrary files
  • Update server with a list of compromised computers
  • Manage registry
  • Download updated copy of itself

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • {BLOCKED}.{BLOCKED}.194.105
  • {BLOCKED}.{BLOCKED}.131.87
  • {BLOCKED}.{BLOCKED}.51.125
  • {BLOCKED}.{BLOCKED}.72.9
  • {BLOCKED}.{BLOCKED}.112.16
  • {BLOCKED}.{BLOCKED}.28.133
  • {BLOCKED}.{BLOCKED}.86.46
  • {BLOCKED}.{BLOCKED}.121.227
  • {BLOCKED}.{BLOCKED}.191.146
  • {BLOCKED}.{BLOCKED}.44.182
  • {BLOCKED}.{BLOCKED}.199.89
  • {BLOCKED}.{BLOCKED}.147.38
  • {BLOCKED}.{BLOCKED}.55.36
  • {BLOCKED}.{BLOCKED}.65.33
  • {BLOCKED}.{BLOCKED}.55.30
  • {BLOCKED}.{BLOCKED}.230.91
  • {BLOCKED}.{BLOCKED}.94.65
  • {BLOCKED}.{BLOCKED}.30.20
  • {BLOCKED}.{BLOCKED}.61.16

Information Theft

This backdoor gathers the following data:

  • Network traffic information
  • Login credentials from FTP, POP3 and SMTP traffic
  • Bitcoins

It attempts to steal stored account information used in the following installed File Transfer Protocol (FTP) clients or file manager software:

  • 32bit FTP
  • 3DFTP
  • ALFTP
  • BitKinex
  • Blaze
  • BulletProof
  • Classic FTP
  • CoffeeCup
  • Core FTP
  • CuteFTP
  • CyberDuck
  • Deluxe
  • Directory Opus
  • ExpanDrive
  • FAR Manager FTP
  • FFFTP
  • FTP Control
  • FTP Explorer
  • FTPGetter
  • FTPRush
  • FileZilla
  • FlashFXP
  • FreeFTP/DirectFTP
  • Frigate3
  • Global Downloader
  • LeapFTP
  • Leech
  • Linas
  • MyFTP
  • NetDrive
  • NetFile
  • Nexus
  • Notepad++
  • NovaFTP
  • Putty
  • Robo
  • SecureFX
  • Sherrod
  • SmartFTP
  • SoftX FTP Client
  • Staff
  • TFTPInfo
  • TurboFTP
  • WISE
  • WebDrive
  • WebSitePublisher
  • WinSCP
  • Windows/Total Commander
  • Wisper/Surfer
  • XFTP

NOTES:

The registry value name {Random value} may be any combination of the following:

  • Checker
  • CrashReport
  • Database
  • Desktop
  • Icon
  • Informer
  • Media
  • Network
  • Notifyer
  • Saver
  • Time
  • Tray
  • Updater
  • Verifyer
  • Video

It saves its updated copy using the following file names:

  • acrord32.exe
  • agent.exe
  • alg.exe
  • ati2evxx.exe
  • avguard.exe
  • batch.exe
  • block.exe
  • ccapp.exe
  • ccevtmgr.exe
  • ccsetmgr.exe
  • convert.exe
  • decompile.exe
  • defwatch.exe
  • dit.exe
  • download.exe
  • dwm.exe
  • edit.exe
  • em_exec.exe
  • explorer.exe
  • extract.exe
  • ezsp_px.exe
  • firefox.exe
  • fix.exe
  • gearsec.exe
  • hkcmd.exe
  • hkcr.exe
  • htpatch.exe
  • ielowutil.exe
  • ieuser.exe
  • iexplore.exe
  • igfxtray.exe
  • isuspm.exe
  • java.exe
  • jqs.exe
  • jucheck.exe
  • jusched.exe
  • khalmnpr.exe
  • klwtblfs.exe
  • lame.exe
  • launch.exe
  • lsass.exe
  • lucoms.exe
  • mac.exe
  • mcshield.exe
  • mcvsescn.exe
  • msascui.exe
  • mscorsvw.exe
  • mspmspsv.exe
  • naprdmgr.exe
  • navapsvc.exe
  • nprotect.exe
  • ntvdm.exe
  • nvsvc32.exe
  • nvxdsync.exe
  • nwiz.exe
  • pctspk.exe
  • pdvddxsrv.exe
  • play.exe
  • point32.exe
  • qbw32.exe
  • qttask.exe
  • rename.exe
  • rundll32.exe
  • services.exe
  • sidebar.exe
  • smc.exe
  • spoolsv.exe
  • svchost.exe
  • taskman.exe
  • terraria.exe
  • toaster.exe
  • trustedinstaller.exe
  • unhide.exe
  • unpack.exe
  • unzip.exe
  • update.exe
  • upgrade.exe
  • uptime.exe
  • view.exe
  • vsmon.exe
  • webscanx.exe
  • winlogon.exe
  • wisptis.exe
  • wmpnetwk.exe
  • wmpnscfg.exe
  • xsd.exe
  • zcfgsvc.exe
  • zumodrive.exe

The downloaded files' folder depends on the Download backdoor command.

This backdoor modifies its file attributes to read-only and hidden after execution.

It uses WinPcap, a legitimate and commonly used Windows packet capture library, to monitor the infected computer's network activities. It does this by dropping and installing the following non-malicious files:

  • %System%\packet.dll
  • %System%\wpcap.dll
  • %System%\drivers\npf.sys

It exchanges encrypted messages with a remote server via HTTP protocol (TCP port 80). It uses the following crafted User-Agent when communicating with the remote host:

  • Mozilla/1.22 (compatible; MSIE 10.0; Windows 3.1)
  • Mozilla/4.0 (compatible; MSIE 10.0; Windows NT 6.1; Trident/5.0)
  • Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:21.0) Gecko/20100101 Firefox/21.0
  • Mozilla/5.0 (Macintosh; Intel Mac OS X 10_6_8) AppleWebKit/537.13+ (KHTML, like Gecko) Version/5.1.7 Safari/534.57.2
  • Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_3) AppleWebKit/534.55.3 (KHTML, like Gecko) Version/5.1.3 Safari/534.53.10
  • Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_6_7; da-dk) AppleWebKit/533.21.1 (KHTML, like Gecko) Version/5.0.5 Safari/533.21.1
  • Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_6_8; de-at) AppleWebKit/533.21.1 (KHTML, like Gecko) Version/5.0.5 Safari/533.21.1
  • Mozilla/5.0 (Windows NT 5.0; rv:21.0) Gecko/20100101 Firefox/21.0
  • Mozilla/5.0 (Windows NT 5.1) Gecko/20100101 Firefox/14.0 Opera/12.0
  • Mozilla/5.0 (Windows NT 5.1; rv:21.0) Gecko/20100101 Firefox/21.0
  • Mozilla/5.0 (Windows NT 5.1; rv:21.0) Gecko/20130331 Firefox/21.0
  • Mozilla/5.0 (Windows NT 5.1; rv:21.0) Gecko/20130401 Firefox/21.0
  • Mozilla/5.0 (Windows NT 6.0; rv:2.0) Gecko/20100101 Firefox/4.0 Opera 12.14
  • Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/28.0.1468.0 Safari/537.36
  • Mozilla/5.0 (Windows NT 6.1; WOW64; rv:21.0) Gecko/20100101 Firefox/21.0
  • Mozilla/5.0 (Windows NT 6.1; WOW64; rv:21.0) Gecko/20130330 Firefox/21.0
  • Mozilla/5.0 (Windows NT 6.1; WOW64; rv:21.0) Gecko/20130331 Firefox/21.0
  • Mozilla/5.0 (Windows NT 6.1; WOW64; rv:21.0) Gecko/20130401 Firefox/21.0
  • Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:22.0) Gecko/20130328 Firefox/22.0
  • Mozilla/5.0 (Windows NT 6.1; rv:21.0) Gecko/20100101 Firefox/21.0
  • Mozilla/5.0 (Windows NT 6.1; rv:21.0) Gecko/20130328 Firefox/21.0
  • Mozilla/5.0 (Windows NT 6.1; rv:21.0) Gecko/20130401 Firefox/21.0
  • Mozilla/5.0 (Windows NT 6.1; rv:22.0) Gecko/20130405 Firefox/22.0
  • Mozilla/5.0 (Windows NT 6.2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/28.0.1464.0 Safari/537.36
  • Mozilla/5.0 (Windows NT 6.2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/28.0.1467.0 Safari/537.36
  • Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/29.0.1547.2 Safari/537.36
  • Mozilla/5.0 (Windows NT 6.2; rv:21.0) Gecko/20130326 Firefox/21.0
  • Mozilla/5.0 (Windows; U; MSIE 9.0; Windows NT 9.0; en-US)
  • Mozilla/5.0 (X11; Linux i686; rv:21.0) Gecko/20100101 Firefox/21.0
  • Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:21.0) Gecko/20100101 Firefox/21.0
  • Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:21.0) Gecko/20130331 Firefox/21.0
  • Mozilla/5.0 (compatible; MSIE 10.0; Macintosh; Intel Mac OS X 10_7_3; Trident/6.0)
  • Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; Trident/4.0; InfoPath.2; SV1; .NET CLR 2.0.50727; WOW64)
  • Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; Trident/5.0)
  • Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; Trident/6.0)
  • Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; WOW64; Trident/6.0)
  • Mozilla/5.0 (compatible; MSIE 8.0; Windows NT 6.0; Trident/4.0; Acoo Browser 1.98.744; .NET CLR 3.5.30729)
  • Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
  • Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.0) Opera 12.14
  • Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0; SLCC2; Media Center PC 6.0; InfoPath.3; MS-RTC LM 8; Zune 4.7)
  • Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0; chromeframe/12.0.742.112)
  • Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 7.1; Trident/5.0)
  • Mozilla/5.0 (iPad; CPU OS 5_1 like Mac OS X) AppleWebKit/534.46 (KHTML, like Gecko ) Version/5.1 Mobile/9B176 Safari/7534.48.3
  • Mozilla/5.0 (iPad; CPU OS 6_0 like Mac OS X) AppleWebKit/536.26 (KHTML, like Gecko) Version/6.0 Mobile/10A5355d Safari/8536.25
  • Opera/9.80 (Windows NT 5.1; U; zh-sg) Presto/2.9.181 Version/12.00
  • Opera/9.80 (Windows NT 6.0) Presto/2.12.388 Version/12.14
  • Opera/9.80 (Windows NT 6.1; U; es-ES) Presto/2.9.181 Version/12.00

This backdoor sends spam email messages using Simple Mail Transfer Protocol (SMTP) connection. It harvests email addresses from the affected computer's local drive.

  SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

10.212.03

FIRST VSAPI PATTERN DATE:

12 Aug 2013

VSAPI OPR PATTERN File:

10.213.00

VSAPI OPR PATTERN Date:

13 Aug 2013

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Scan your computer with your Trend Micro product and note files detected as BKDR_KELIHOS.CEW

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

Delete this registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • {Random Value} = "{Malware Path and File Name}"

Step 5

Search and delete these files

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %System%\packet.dll
  • %System%\wpcap.dll
  • %System%\drivers\npf.sys

Step 6

Search and delete the file detected as BKDR_KELIHOS.CEW

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden files in the search result.

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_KELIHOS.CEW. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.


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